The present invention generally relates to the field of aquatic floatation and transportation systems. More particularly, the invention relates to a foot-wearable human floatation apparatus used primarily for water-walking or water-skating, and a propulsion mechanism therefor.
Walking on water, like flying, has been considered an interesting mode of transportation for centuries, if not millennia. Prior attempts at creating a foot-worn floatation/propulsion system have yet to produce a water-walking apparatus that enables a human to take near-normal walking steps with confidence.
The act of walking, on land or on water, can be broken down into a sequence of coordinated basic movement pairs (each pair comprising a left leg movement and a right leg movement). There are four basic movements: Forward, an actual forward movement of the first leg and foot; Backwards, the backwards push against the resistance of the ground during which the second foot does not actually move; Up, the lifting the first leg off the ground or un-weighting of the leg during skating; and Down, applying one's weight on the first leg. The act of walking naturally requires the smooth transition from one action to the next, and from one leg to the next. Any water-walking apparatus should allow for all four movements in the normal sequence and with the natural timing a human has learned when walking on land. A key consideration in walking on any medium is to emulate the assumed “100%” friction typically found when applying the Backwards movement on land. Humans slip and fall when friction is reduced during that portion of the walking cycle. In addition, a water-walking apparatus should allow a user to “step around” a turn as a way to change directions while providing the user a feeling of stability at least somewhat similar to the stability found on solid ground. Thus, a successful water-walking apparatus should limit pitch, roll, and side-to-side motions transmitted from the float to the user without constraining the natural walking up-down, front-back, and yawing motions transmitted from the user to the float.
Skating is different than walking in several ways. Skating is a series of movements optimized for low foot-to-support medium friction situations (ice, roller blades, water), where sliding a foot across the support medium will not completely halt forward progress. Because of the low friction, the Up movement doesn't necessarily imply lifting the foot—a simple easing of the pressure to reduce the (normal force generated) frictional resistance, as in Nordic skiing, is often adequate. Second, skating typically involves a gliding movement; weight is carried on the forward leg while the back leg “pushes off”. The person using a skating apparatus lifts the foot that has just finished the Backwards, power movement and lets himself be carried forward by momentum, weight on the forward leg. Depending on the desired speed, the user either continues the one leg glide, brings the rearward foot parallel with the gliding foot and performs a two footed glide, or brings the rearward foot to the forward position in anticipation of the next pushing movement. Note that the skater can alternate the roles of the left and right legs (the normal skating action) or repeatedly use only one leg as the pushing leg (as in powering a scooter).
A typical prior water walking apparatus comprises two elongated floats and some sort of variable resistance propulsion mechanism, typically comprising a multitude of either small rotatable flaps or fixed, rearward facing cups, pouches, or scoops. The typical prior float is generally flat bottomed and straight sided and the typical prior propulsion mechanism does not provide maximum resistance against the water at the point in the walking cycle when it is needed; specifically, the maximum resistance is needed at the beginning of the Backwards (power) movement. Prior propulsion systems either require the user to wait to take each step or allow backwards slippage. For example, U.S. Pat. No. 4,698,039 teaches an apparatus having a pair of symmetric floats, these floats being generally rectangular in cross-section and having a flat bottom over most of their length. Additionally, the '039 patent teaches the use of a series of rotatable flaps with vertical axes spaced along either side of a central keel. The flaps move into their high resistance position only by the rearward slippage at the beginning of each step. Further, each flap is “shadowed” by the flap next in line, greatly reducing their propulsive power. Another attempt to provide a propulsion system with rotatable flaps with vertical axes is described in U.S. Pat. Nos. 4,261,069 and 4,117,562, both by Schaumann. In the '069 patent there are two flaps in series in a tunnel like chamber, completely obviating the functionality of the front flap for pushing backwards against the water. The overall float shape in both these patents is again generally an elongated rectangle. The '069 patent is notable in use of a resilient stop that both prevents the flap from opening beyond the desired point and provides a small push back toward the closed condition. However, the resilient stop only provides an initial push, the energy of which is quickly absorbed by the resistance of the water. Two examples of “horizontal” (viz., having a horizontal axis) flaps or pouches are provided by U.S. Pat. Nos. 5,593,334 and 5,697,822. Again, the linear series of small pouches or flaps are too small to be effective and are self-obviating because of shadowing, and again the float shape is generally conducive to instability.
Some prior devices include a tethering mechanism to keep the floats from separating. Many of these mechanisms are overly constraining—that is, rather than just preventing excessive transverse separation, they instead prevent the user's feet from moving in at least some of the degrees of freedom possible on land. Typically, the tether mechanism, if present, either inhibits a full and natural stride (i.e., the length of a step), introduces friction into what is normally a frictionless forward leg movement, prevents the redirection of a forward stride (yaw) (as is needed for turning), or inhibits the required Up and Down leg movements. For example, the '069 patent includes an intertwined cable tether whose claimed function is explicitly to eliminate virtually all sideways motions, to limit the length of the stride, and to ensure the engagement of a tongue-and-groove mechanism for eliminating up-down motions. Another example of an overly constraining tethering mechanism is shown in U.S. Pat. No. 3,121,892 in which the two floats (actually “skis” in that each float is a thin, flat board similar to conventional water skis) are joined by what amounts to either a single or a double linear bearing that constrains the relative motion between the skis.
It is therefore an object of this invention to provide a water-walking apparatus in which the maximum resistance to the water is achieved at the beginning of, and maintained throughout, the Backward pushing movement. Other objectives can include providing an apparatus in which the user achieves a near land-like stability, which allows the user to transition from deep to shallow water and thence to solid surfaces (land, ice, etc.) while walking, and/or an apparatus with a foot attachment method that allows the user all normal walking motions while providing a quick release for safety. These and other objectives are met through the various embodiments discussed below.